Recently, for the cooling of semiconductor devices (for example, thyristors for power conversion, diodes, etc.), heat sinks utilizing the excellent heat transfer performance and excellent heat-in and heat-out capabilities of heat pipes have come to be used. These heat sinks have better radiation characteristic than conventional air cooled heat sink made of extrusion and water cooled heat sinks, etc. and are reduced in size and weight. As shown in FIGS. 1(A) and (B), such heat sinks have a construction wherein the heat-in sections (3) of the plural heat pipes (2) arranged parallel in a row are inserted into a block (1) on which a semiconductor device (a) is mounted. A large number of radiating fins (5) crossing over the heat pipes (2) at right angles thereto are fitted to the heat-out sections (4) of the heat pipes (2) protruding from the block (1) in a row.
For the block (1) and the fins (5), copper or aluminum is used, and for the heat pipes (2), copper-water type or aluminum-freon type is used. Ordinarily, as shown in FIG. 2, two heat sinks are combined in parallel. Electrical insulating plates (6), (6'), and (6") are arranged between the fins 5 of each heat sink. The semiconductor device (a) is put between block (1) and a parallel block (1'). The heaat-in sections (3) and (3') of the heat pipes (2) and (2') are inserted in the blocks (1) and (1'), respectively. The heat generated from the semiconductor device (a) is transferred to the heat pipes (2) and (2') through the blocks (1) and (1'), and allowed to radiate from the fins (5) and (5') fitted to the heat-out sections (4) and (4') of the heat pipes (2) and (2'), respectively. The coaling rate is increased by sending air in the direction A indicated by an arrow in FIG. 1.
With regard to the insertion of the heat pipes (2) into the block (1), in order to keep the thermal resistance from the semiconductor device (a) to the minimum, the heat pipes (2) are fitted so as to be brought close to a minimum distance capable of maintaining a fixed degree of mechanical strength against the plane of the block (1) where the semiconductor device (a) is mounted. The heat pipes (2) are inserted in a row in the block (1) at appropriate pitch intervals.
Moreover for the radiation of large-capacity semiconductor devices, the heat sinks are used as shown in FIGS. 3(A) and (B). That is, the plural heat pipes (2) are arranged in parallel in two rows, the heat-in sections (3) thereof being inserted into the block (1), and a large number of fins (5) crossing over the heat pipes (2) at right angles thereto are fitted to the heat-out sections (4) of the heat pipes (2) protruding from the block (1) in two rows.
Although all of these heat pipe heat sinks show better radiation characteristics compared with the conventional air cooled heat sink made of extrusion and water cooled heat sink, etc., further improvement has been desired.